Self-Supplying of Hydrogen Peroxide/Oxygen Based on CaO₂-Co₃O₄ Cascade Nanoreactors for Cellular Microenvironment Regulation

Monitoring and regulating levels of hydrogen peroxideand oxygenin cells can provide valuable information for cancer diagnosis, treatment,and development. However, it remains a significant challenge. In thisstudy, a new nanocomposite (CaO2-Co3O4@HA) was developed by combining CaO2 nanoparticles andCo(3)O(4) nanopolyhedrons and functionalizationwith hyaluronic acid (HA). The resulting nanoreactor can dynamicallyregulate contents of hydrogen peroxide and oxygen in cells. Due tothe presence of HA, the synthesized CaO2-Co3O4@HA has good biocompatibility and active targeting ability.The CaO2 nanoparticles produce enough H2O2 in a slightly acidic (pH 6.5) environment, while the Co3O4 nanopolyhedrons with good catalase (CAT) mimicactivity can effectively catalyze H2O2 intoO(2). The CaO2-Co3O4@HAthen acted as a cascade nanoreactor for the self-supplying of hydrogenperoxide/oxygen. The process was monitored using H2O2 and O-2 fluorescence probes and confirmed by fluorescencespectra and fluorescence confocal microscopy. This study not onlyverifies that the nanoreactor has a high ability to self-supply H2O2 and catalyze the generation of oxygen via themetal oxides under slightly acidic conditions but also provides anew way to regulate the contents of oxygen and hydrogen peroxide incells. The tandem nanoreactor may have potential implications forcancer diagnosis and treatment through the regulation of reactiveoxygen species in the cellular microenvironment.